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Discussion Starter · #1 ·
Sorry if this is posted in the wrong section as i am new to the FJ forum and ownership of my new to me 2008 Trail Team FJ 6MT. Upon purchase of this i tried to get the diff lock to work as it always has in my Tacomas and 4Runners but in 4 LO moving sitting ect it doesnt do anything what so ever. I dont even get a flashing light on the dash indicating that its trying to engage. Out of all diff lock issues ive ever had i always have had a flashing rr diff lock light even it they werent engaging. Please if anyone has had this issue or anyone can point me in the right direction it would be extremely helpful. No blown fuses btw
 

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Sorry if this is posted in the wrong section as i am new to the FJ forum and ownership of my new to me 2008 Trail Team FJ 6MT. Upon purchase of this i tried to get the diff lock to work as it always has in my Tacomas and 4Runners but in 4 LO moving sitting ect it doesnt do anything what so ever. I dont even get a flashing light on the dash indicating that its trying to engage. Out of all diff lock issues ive ever had i always have had a flashing rr diff lock light even it they werent engaging. Please if anyone has had this issue or anyone can point me in the right direction it would be extremely helpful. No blown fuses btw
Does it ever engage? Like from a dead stop. Is the position switch working at the diff? If you pull the lock does it visually move when you operate it at the dash?
 

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Wrong answer. Get off the light on the dash, it's taking you down the wrong path right now. Hold the locking assembly in your hand and have someone work the switch. What happens?
 

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Discussion Starter · #5 ·
Wrong answer. Get off the light on the dash, it's taking you down the wrong path right now. Hold the locking assembly in your hand and have someone work the switch. What happens?
ill check when i get home but no sound at all like with previous toyotas
 

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Discussion Starter · #6 ·
Wrong answer. Get off the light on the dash, it's taking you down the wrong path right now. Hold the locking assembly in your hand and have someone work the switch. What happens?
Another issue i found the wiring diagram that operates everything. I found 2 factory wires cut directly under the clutch master cylinder inside the main wire harness coming from the fuse box in the engine bay white with black stripe and green with red stripe wondering who cut it and why?
 

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You need to splice the cut wires before getting into deeper troubleshooting. I assume that all fuses in both fuse panels have been checked.

White with black stripe is universally a ground wire in FJ schematics. Green with red is used in a number of circuits with widely different functions ... if this vehicle is new to you, check the functions of the following circuits and systems, as they all use 'green with red stripe' wiring:
a) Horn relay
b) Park-Neutral switch and shift lock ECU
c) Airbag sensor and driver's seatbelt buckle switch
d) RH rear view mirror adjustment motor

Very frequently your problem with a non-functional diff lock is caused by a defective L4 sensing switch on the transfer case. If this switch doesn't close, the 4WD ECU never sends a command to the RR diff lock actuator to lock. Transfer case oil seeps past a rubber diaphragm in the switch and contaminates the electrical contacts.

With engine off, try shifting the transfer case abruptly from 4H to 4L range 25-50 times; sometimes this will scrub contamination off the switch contacts and then the switch will work for a while.

If 'exercising' the switch doesn't seem to make any difference, get under the vehicle, disconnect the switch from the wiring harness, and measure the resistance across the switch contacts. Switch open (H4 range) the resistance should be multi-megohms; switch closed, the resistance should be less than 1 ohm. If the resistance stays high at all times, the switch will need to be replaced.

Here's a detailed failure analysis of one of these switches - I have seen at least three of these switches fail in the identical manner.

Failure analysis: failed transfer case switch =...
 

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Discussion Starter · #8 ·
Very frequently your problem is caused by a defective L4 sensing switch on the transfer case. If this switch doesn't close, the 4WD ECU never sends a command to the RR diff lock actuator to lock. Transfer case oil seeps past a rubber diaphragm in the switch and contaminates the electrical contacts.

With engine off, try shifting the transfer case abruptly from 4H to 4L range 25-50 times; sometimes this will scrub contamination off the switch contacts and then the switch will work for a while.

If 'exercising' the switch doesn't seem to make any difference, get under the vehicle, disconnect the switch from the wiring harness, and measure the resistance across the switch contacts. Switch open (H4 range) the resistance should be multi-megohms; switch closed, the resistance should be less than 1 ohm. If the resistance stays high at all times, the switch will need to be replaced.

Here's a detailed failure analysis of one of these switches - I have seen at least three of these switches fail in the identical manner.

Failure analysis: failed transfer case switch =...
Ill try that now stuck at work tonight until after dark but have the next 4 hours free this would explain why there is no dash light also... thanks so much for the input
 

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Discussion Starter · #9 ·
Ill try that now stuck at work tonight until after dark but have the next 4 hours free this would explain why there is no dash light also... thanks so much for the input
no luck at all.. atrac works fine no rr lock
 

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Gotta ask.....is the switch plugged in?
 

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Just wanted to pop in and say welcome!

Good luck with your issue!
🍻 🍻🍻🍻
 

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Discussion Starter · #13 ·
So after further investigation everything is plugged in but someone prior to me has cut 3 wires of the harness inside the drivers side kick panel. none of these wires being white/blue for the rr lock anytime mod. I figured this out as i was going to do that mod to see if the locker would work then. There is no blue box inside my 2008 TT driver kick panel nor passenger side. Could anyone tell me where this blue box could be located to bypass the 4lo in my 08 TT 6MT??
 

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Discussion Starter · #14 ·
Or is there a complete wire diagram for this in tech notes somewhere where i can figure out what all these cut wires with no ends are for? I cant find where the opposite cut ends are like there are 3 wires with no place to reconnect feeling very frustrated i cant stand it when people cut up a perfectly good FJ
 
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